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  1. //Matthew Santos    CS1A     Ch. 6, Pg. 373, #15
  2. /***********************************************
  3.  * 
  4.  * CALCULATE POPULATION
  5.  * _____________________________________________
  6.  * Calculates and displays the population size
  7.  * over any number of years based off the
  8.  * starting size and annual birth and death rate.
  9.  * _____________________________________________
  10.  * INPUT
  11.  *      startingPop : starting population
  12.  *      birthRate   : birth rate as a decimal
  13.  *      deathRate   : death rate as a decimal
  14.  *      years       : years simulated
  15.  * 
  16.  * OUTPUT
  17.  *      population for the given years
  18.  ***********************************************/
  19. #include <iostream>
  20. #include <iomanip>
  21. using namespace std;
  22.  
  23. double calculatePopulation(double, double, double);
  24.  
  25. int main() {
  26.     double startingPop;
  27.     double birthRate;
  28.     double deathRate;
  29.     int years;
  30.  
  31.     // Input for starting population
  32.     cout << "Enter the starting size of the population: ";
  33.     cin >> startingPop;
  34.     while (startingPop < 2)
  35.     {
  36.         cout << "Starting size must be at least 2. Enter again: ";
  37.         cin >> startingPop;
  38.     }
  39.  
  40.     // Input for birth rate
  41.     cout << "Enter the annual birth rate (as a decimal, example 0.05 for 5%): ";
  42.     cin >> birthRate;
  43.     while (birthRate < 0)
  44.     {
  45.         cout << "Birth rate cannot be negative. Enter again: ";
  46.         cin >> birthRate;
  47.     }
  48.  
  49.     // Input for death rate
  50.     cout << "Enter the annual death rate (as a decimal, example 0.02 for 2%): ";
  51.     cin >> deathRate;
  52.     while (deathRate < 0)
  53.     {
  54.         cout << "Death rate cannot be negative. Enter again: ";
  55.         cin >> deathRate;
  56.     }
  57.  
  58.     // Input for number of years
  59.     cout << "Enter the number of years to display: ";
  60.     cin >> years;
  61.     while (years < 1)
  62.     {
  63.         cout << "Number of years must be at least 1. Enter again: ";
  64.         cin >> years;
  65.     }
  66.  
  67.     // Display the population each year
  68.     cout << fixed << setprecision(0);
  69.     cout << "\nYear\tPopulation\n";
  70.     cout << "-----------------\n";
  71.  
  72.     double population = startingPop;
  73.     for (int year = 1; year <= years; ++year)
  74.     {
  75.         population = calculatePopulation(population, birthRate, deathRate);
  76.         cout << year << "\t" << population << endl;
  77.     }
  78.  
  79.     return 0;
  80. }
  81.  
  82. double calculatePopulation(double P, double B, double D)
  83. {
  84.     return P + (B * P) - (D * P);
  85. }
Success #stdin #stdout 0.01s 5320KB
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stdin
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500 0.07 0.02 10
stdout
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Enter the starting size of the population: Enter the annual birth rate (as a decimal, example 0.05 for 5%): Enter the annual death rate (as a decimal, example 0.02 for 2%): Enter the number of years to display: 
Year	Population
-----------------
1	525
2	551
3	579
4	608
5	638
6	670
7	704
8	739
9	776
10	814
https://ideone.com/EGpQ49
language:
C++ (gcc 8.3)
created:
15 days ago
visibility:
public

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